Applications of various LED goods, such as traffic signs, motorcycle tail lights, automobile head lights, street lamps, computer indicators, flashlights, LED backlight sources, etc., can now be seen in daily life. In addition to the chip process, almost all of these products are gone through packaging procedure as well.
FIG. 1 shows a conventional process of LED assemblies. First, a sapphire substrate 10 is provided. Subsequently, semiconductor fabrication processes like epitaxial process, thin film deposition, lithography and etching are performed to form multiple LED chips on the sapphire substrate 10, as the wafer 12 shows. Each LED chip may have one or more LED units, and each LED unit comprises a light-emitting layer. In the light-emitting layer, light is emitted due to recombination of electrons and holes. Each wafer 12 is examined by the wafer acceptance test (WAT) first, and then the qualified wafer 12 is cut to form individual LED chips. The LED chip is also referred as LED die. Each LED chip is inspected and classified according to the photoelectric characteristics thereof, such as forward voltage, dominant wavelength, luminous intensity, etc. LED chips have same photoelectric characteristic are picked and placed on a temporary carrier film, and the temporary carrier film may be a blue tape or a tape-on-reel having a surface for the chips to be mounted thereon. In FIG. 1, three different kinds of LED chips are placed on the temporary carrier films B1, B2 and B3, respectively. LED packaging manufacturers purchase temporary carrier films with LED chips and produce LED assemblies after appropriate packaging process. For example, the LED assembly 14 in FIG. 1 comprises an LED chip 16, a cooling base 18, bonding wires 20, silicone 22 and a lens 24.
Nevertheless, the process of removing LED chips one by one from a temporary carrier film and to fix them to the base of a LED product is usually very time consuming.